The specific aims grow out of our previous case/control and longitudinal study of psychosocial factors in the course of a chronic pain disorder, the temporomandibular pain and dysfunction syndrome (TMPDS). The aims center on unresolved questions about the extent and nature of the relationships between a specific chronic pain syndrome of unknown origin and depression. In our previous study of 151 TMPDS cases and 139 well controls, one striking finding was the much higher level of psychological distress observed in the pain cases by contrast with the controls. In a separate pilot study on a sample of 20 of these cases, a psychiatrist and clinical psychologist conducted rigorous research diagnostic interviews and made diagnoses of DSM-III-R psychiatric disorders, including past and current major depression. It is the high rate of major depression that they found that provides the point of departure for the proposed research. We now propose to conduct two interviews with a new and larger sample of 160 cases and 160 controls and 320 of their first degree relatives. The first interview, conducted by psychiatrists and clinical psychologists, would assess rates of major depression and other DSM-III-R disorders in probands and all their adult first degree relatives by interviewing probands and one of their first degree relatives. The second interview, conducted by masters level health professionals, would assess family history of chronic pain symptoms and serious physical illnesses in probands and all their adult first degree relatives by interviewing probands and one of their adult first degree relatives by interviewing probands and one of their first degree relatives. Rates of depression and pain in subgroups of depressed vs. nondepressed pain patients and controls will be examined to elucidate the temporal relationship between pain and depression. Plans for statistical analyses include calculation of odds ratios to assess the comorbidity of TMPDS and major depression, and logistic regression to predict case status from the presence of pain disorders and/or major depression in first degree relatives.